Source: Semiconductor Industry Observation
History of Semiconductor Development
1. Semiconductors are the foundation of information technology. The invention of large-scale integrated circuits, semiconductor lasers, and various semiconductor devices in the last century played a crucial role in the modern information technology revolution, triggering a new global industrial revolution. Information technology is the major trend in today’s world economy and social development, and the level of informatization has become an important indicator of modernization for countries and regions.
As we enter the 21st century, the world is accelerating its pace of informatization. Driven by the needs of the information technology revolution, semiconductor physics, materials, and devices will see new and faster developments. The size of integrated circuits will continue to shrink, leading to the emergence of new quantum effect devices; wide bandgap semiconductors represent a new direction with broad applications in short-wavelength lasers, white light-emitting diodes, and high-frequency high-power devices; nano-electronic devices may serve as the next generation of semiconductor microelectronics and optoelectronic devices; utilizing single electrons, single photons, and spin devices for quantum control will play a key role in the practical application of quantum computing and quantum communication.
2. Invention of the Transistor. In 1945, at the end of World War II, the president of Bell Labs, William Shockley, decided to establish a solid-state physics group to adapt the lab’s work from wartime to peacetime needs, with John Bardeen and Walter Brattain as members. Shockley and Bardeen were theoretical physicists, Brattain was an experimental physicist, and their combination of expertise was a golden match for semiconductor physics research and the invention of the transistor. They focused on the study of semiconductor materials silicon and germanium from the very beginning.
During World War II, the British used radar to detect German bombers. The core of radar was the vacuum tube, which could amplify weak currents. Shockley had been preparing to create a solid-state device capable of amplifying current to replace vacuum tubes since 1939. In December 1947, Bardeen and Brattain created the world’s first germanium point-contact transistor, which had current amplification capabilities.
The results of Bardeen and Brattain were published in June 1948. Although the invention of the point-contact transistor opened the door to the development of transistors, its complex structure, poor performance, large size, and manufacturing difficulties limited its industrial promotion and application, resulting in a weak societal response.
In January 1948, based on his research on p-n junction theory, Shockley invented another type of planar junction transistor and obtained a patent in June 1948. The planar junction transistor, also known as the field-effect transistor, is planar in shape and can be mass-produced using various planar processes (such as diffusion and masking). Only after the invention of the planar junction transistor did the superiority of transistors become widely recognized, gradually replacing vacuum tubes.
Due to the contributions of Bardeen, Brattain, and Shockley in the invention of the transistor and junction transistor, they were awarded the Nobel Prize in Physics in 1956. The first application of the semiconductor transistor was in Sony’s portable radio, which became a global sensation and generated significant profits.
3. Invention of the Integrated Circuit. Transistor radios are much smaller than vacuum tube radios and can be carried around. However, they consist of transistors, resistors, capacitors, and magnetic antennas soldered onto a circuit board, connected by wires, making them still relatively large and complex to assemble.
In 1958, the U.S. government established a fund for the miniaturization of transistor circuits to meet the needs of the U.S. in catching up with the Soviet Union’s launch of the first artificial satellite. At that time, Jack Kilby of Texas Instruments undertook this task, attempting to create a miniaturized circuit that packaged transistors, resistors, and capacitors together. In September 1958, Kilby created the world’s first integrated circuit oscillator, which he documented in his notes that day. Kilby’s integrated circuit was patented in February 1959, named “miniaturized electronic circuit.”
Meanwhile, Robert Noyce of Fairchild Semiconductor in California proposed the idea of connecting transistors with aluminum. Five months after Kilby’s invention of the integrated circuit, in February 1959, he used the planar transistor method proposed by Horn to generate an SiO2 mask over the entire silicon wafer, applying photolithography to create windows and lead paths, diffusing impurities through the windows to form the base, emitter, and collector, and evaporating gold or aluminum to create the integrated circuit. Noyce’s integrated circuit was patented in July 1959, named “semiconductor device and lead structure.” This marked the beginning of a new era of large-scale development for integrated circuits.
4. Invention of the Solar Cell. To meet the needs of artificial satellites, in 1954, Pearson and Fuller used diffusion techniques of phosphorus and boron to create large-area silicon p-n junction solar cells with a photoelectric conversion efficiency exceeding 6%, which was 15 times better than the previous best solar conversion efficiency. Its low production cost allowed for mass production, leading to widespread application.
The working principle of solar cells is the photovoltaic effect. When light strikes a semiconductor, it generates electron-hole pairs within the semiconductor. If an external circuit is connected, current will flow, which is the photovoltaic effect.
The commercial application of solar cells began in 1958 when they were selected as the power source for the radio transmitter of the United States’ first artificial satellite, Vanguard I. In the current energy crisis, solar cells have attracted significant attention as a renewable and pollution-free power source.
5. Invention of the Semiconductor Laser. The working principle of semiconductor light-emitting diodes and lasers is the opposite of that of solar cells: solar cells generate electricity from light, while light-emitting diodes and lasers generate light from electricity. By injecting current, electrons and holes are introduced into the conduction and valence bands of the semiconductor. When electrons and holes recombine, they produce photons.
In 1962, Hall in the U.S. created the first semiconductor laser using a p-n homojunction. To generate laser light, three conditions must be met: population inversion, a resonant cavity, and current exceeding a certain threshold.
In 1963, Kremer in the U.S. and Alferov in the Soviet Union independently created heterojunction lasers, where the junction region used a material with a smaller bandgap, such as GaAs, while the p and n regions used materials with larger bandgaps, such as AlxGa1-xAs. This effectively confined the light-emitting region to a narrow junction area, significantly improving light-emitting efficiency and reducing the threshold current for lasers. In 1970, the Soviet Union’s Yoffe Institute and Bell Labs in the U.S. each developed a dual heterojunction laser that operated continuously at room temperature, leading to widespread applications of semiconductor lasers in optical communication.
Due to Kremer and Alferov’s significant contributions to the development of semiconductor lasers, they, along with integrated circuit inventor Kilby, were awarded the Nobel Prize in Physics in 2000. The invention of silicon large-scale integrated circuits and semiconductor lasers ushered the world into an information age based on microelectronics and optoelectronics, greatly promoting social and economic development.
6. Invention of Molecular Beam Epitaxy Technology. A key technology for manufacturing dual heterojunction lasers is molecular beam epitaxy. In 1968, Bell Labs’ Y. H. Chen discovered that by finely controlling the beam flow size and time in an ultra-high vacuum chamber, it was possible to grow different layers and types of semiconductor materials as needed, thus inventing molecular beam epitaxy technology. A schematic diagram of the molecular beam epitaxy device is shown. The device operates under ultra-high vacuum conditions (10-10 torr), with the evaporation furnace containing source materials (such as Ga, As, Al, etc.). A controllable shutter is positioned in front, which, when opened, directs the evaporated source atoms straight onto a heated substrate for epitaxial growth. Currently, this technology can achieve single atomic layer growth. The device is surrounded by various detection instruments to monitor the growth process.
Applications of Semiconductor Technology
1. Large-Scale Integrated Circuits and Computers. Large-scale integrated circuits lay the foundation for the development of computers and networks. According to Moore’s Law, the integration of integrated circuits doubles every 18 months, and recently, their line width has reached tens of nanometers (millimeters, micrometers, nanometers), with each chip containing hundreds of billions of components. Computer science has reached a high level, with both hardware and software being highly mature, and computers capable of trillions of operations per second (e.g., Tianhe: 20 trillion operations, second in the world) have emerged, providing powerful tools for high-speed calculations and massive information processing and conversion.
Since the birth of computers in 1943, the invention of integrated circuits has rapidly advanced computers towards high-speed operation and miniaturization. Currently, major developed countries and China possess large computers capable of over 100 trillion floating-point operations. China ranks second in the world in the number of such supercomputers, second only to the United States. These supercomputers can be used for protein analysis, new drug development, and military applications such as simulating nuclear explosions and code-breaking. It is worth noting that China is still lagging in the large-scale integrated circuits required to manufacture these computers, with most still needing to be imported.
2. Optical Communication Technology. Previously, long-distance communication relied on long-distance telephones or telegraphs, which were expensive due to the low number of calls. In 1966, K. C. Kao of the British Standard Communication Laboratory proposed using high-purity, high-transparency glass fibers to transmit laser signals. If the loss could be reduced to 20 decibels per kilometer, long-distance optical communication could be achieved. In 1970, R. D. Maurer and others at Corning Glass in New York used a “deposition process” to create dense glass tubes by hydrolyzing silicon tetrachloride vapor in a flame, which were then heated and drawn into fine glass fibers. The birth of low-loss glass fibers marked a milestone in optical communication technology.
In 1976, Bell Labs conducted the first field experiment of optical communication in Atlanta, achieving excellent results. The average power loss of the optical fiber was 6 decibels per kilometer, with error-free transmission of information exceeding 10.9 kilometers, equivalent to 17 loops around the optical fiber. In December 1976, Bell Labs announced that optical wave communication had passed its first test, proving the feasibility of optical wave communication. This marked the beginning of the optical communication era and signaled the formal transition from the microelectronic age to the optoelectronic age.
Today, telecommunications networks, computer networks, and cable television networks have become important infrastructures for a country, with all political, economic, military, scientific, and technological activities, as well as daily life, relying on these three networks. China currently has 850 million telephone users, including 480 million mobile phone users, making it the largest telecommunications network in the world. The number of internet users has reached 137 million, and cable television users have reached 130 million, accounting for one-third of the world. The future trend is the integration of these three networks. Mobile internet access has become common, with companies like Apple’s leading the way.
3. Wireless Communication Technology (Mobile Phones). The foundation of wireless communication is the cellular mobile phone system, which was first introduced by Bell Labs in 1978 with the Advanced Mobile Phone Service (AMPS) system. This system divides the service area into many small hexagonal geographic areas (cells), resembling a honeycomb. Each cell contains low-power wireless telephone transmitters, receivers, and a control system, forming a base station. The base stations of different service areas are connected to a central switching entity (mobile telephone exchange) via optical fibers, which houses an electronic switching system. The base station network tracks the location of mobile terminals, allowing them to automatically reconnect with neighboring base stations when they enter another cell to continue calls. Since the wireless call power within a cell is low, it only affects a limited range, preventing interference with communication signals from other cells.
The first AMPS system was successfully tested in Chicago in July 1979. In April 1992, AT&T’s Microelectronics Group announced the production of integrated circuit chips for the next generation of digital cellular phones, making the company a leading supplier of digital signal processing components for mobile communications. This digital signal processor formed the DSP1600 series, significantly reducing the size and power of mobile phones, making them very popular in the market.
In addition to mobile phone communication, there are other wireless communication methods, including satellite transmission of high-definition television, inter-satellite communication, multipoint video communication, wireless local area networks, communication between vehicles, and collision avoidance radar, all operating in the microwave frequency range from several GHz to 100 GHz.
4. Semiconductor Solar Cells – Silicon Materials for Solar Cells. The silicon materials used for solar cells mainly include: single crystal silicon, amorphous silicon, ribbon silicon, and thin-film polycrystalline silicon. The efficiencies of solar cells made from these materials in laboratories and industries are shown. Currently, cast polycrystalline silicon accounts for 47.54% of solar cell materials, making it the most significant solar cell material. By 2004, the market share of cast polycrystalline silicon had exceeded 53%. Single crystal silicon accounted for 35.17%, ranking second, while amorphous silicon thin films accounted for 8.3%, ranking third, and compound semiconductors CuInSe and CdTe only accounted for 0.6%.
5. Semiconductor Solar Cells – Polycrystalline Silicon Solar Cells. Until the 1990s, the solar photovoltaic industry was primarily based on single crystal silicon. Although the cost of single crystal silicon cells has been continuously decreasing, they still lack competitiveness compared to conventional electricity, making cost reduction a goal pursued by the photovoltaic industry. Since the invention and application of cast polycrystalline silicon in the 1980s, it has grown rapidly. With its relatively low cost and high efficiency, it has continuously encroached on the market share of single crystal silicon, becoming the most competitive solar cell material. By the early 21st century, it accounted for over 50% of the market and has become the primary solar cell material.
6. Semiconductor Solar Cells – Amorphous Silicon Thin-Film Solar Cells. Today, amorphous silicon thin-film solar cells have developed into one of the practical and inexpensive types of solar cells, with considerable industrial scale. The total production capacity of amorphous silicon solar cells worldwide has reached over 50 MW annually, with sales of components and related products exceeding $1 billion. Their applications range from small devices like watches and calculators to large independent power stations of 10 MW, significantly promoting the development of solar photovoltaics.
Compared to crystalline silicon, amorphous silicon thin films have advantages in preparation processes, low costs, and the ability for large-scale continuous production. In the field of solar cells, these advantages are specifically manifested as:
- Low material and manufacturing process costs. This is because amorphous silicon thin-film solar cells are prepared on inexpensive substrate materials such as glass, stainless steel, and plastic, which are low-cost; moreover, amorphous silicon thin films are only a few thousand angstroms thick, less than one percent of the thickness of crystalline silicon cells, significantly reducing the cost of silicon raw materials; furthermore, amorphous silicon is prepared at low temperatures, with deposition temperatures of 100°C to 300°C, which clearly reduces energy consumption in large-scale production, greatly lowering costs.
- Easy to form large-scale production capacity.
- Diverse varieties and applications.
- Easy to achieve flexible batteries. Amorphous silicon can be prepared on flexible substrates, and its silicon mesh structure has unique mechanical properties, allowing it to be made into lightweight, flexible solar cells that can be easily integrated into buildings and various daily products.
However, compared to crystalline silicon, amorphous silicon solar cells have relatively low efficiency, with the stable highest conversion efficiency of laboratory cells only around 16%; on production lines, the efficiency does not exceed 10%; moreover, the photoelectric conversion efficiency of amorphous silicon solar cells significantly degrades under long-term exposure to sunlight, and this issue has not yet been fundamentally resolved.
7. Semiconductor White Light Lighting. 1. Significance of Developing Semiconductor White Light Lighting Gallium nitride light-emitting diodes (LEDs) are efficient, long-lasting solid-state lighting sources. Incandescent and fluorescent lamps are currently the most widely used traditional white light sources. Incandescent lamps are thermal light sources (color temperature 2800K), containing a large amount of infrared radiation, with short lifespans and low luminous efficiency, while fluorescent lamps are cold light sources, highly efficient but short-lived and toxic (containing mercury). Compared to traditional incandescent and fluorescent lamps, gallium nitride LEDs are solid-state lighting cold light sources with characteristics such as small size, light weight, low voltage, high efficiency, and long lifespan, making them energy-saving and environmentally friendly lighting sources.
Gallium nitride LEDs are now used in many applications: landscape lighting, traffic lights, car tail lights, and large-screen display lights. Energy is an essential element for the sustainable development of the economy and society, and saving energy and improving energy efficiency are major strategies for sustainable energy development. Statistics show that global lighting consumes about 20% of total electrical power. Due to the high efficiency of LEDs, LED white light lighting can save a significant amount of coal and oil used for power generation, potentially reducing global CO2 emissions by 2.5 billion tons annually. Therefore, gallium nitride LED white light lighting has enormous market potential, and once cost and efficiency issues are resolved, it could replace the currently widely used incandescent and fluorescent lamps, triggering a revolution in white light lighting technology.
2. Technical Approaches for Gallium Nitride LED White Light Lighting It is well known that white light can be synthesized from the three primary colors: red, green, and blue. Gallium nitride LEDs generally emit light of only one color. White light illumination must also be achieved through the synthesis of RGB primary colors. The RGB primary colors can be directly emitted by LEDs or can be obtained by using LEDs to excite fluorescent materials, resulting in secondary light conversion to obtain the three primary colors or quasi-primary colors.
3. Development Directions for LED White Light Lighting Technology
- Research and develop near-ultraviolet and deep-ultraviolet LED devices to achieve high color rendering index “solid white light fluorescent lamps.” This white light technology has high color rendering index (CRI > 90), high conversion efficiency (external quantum efficiency 43%), and high color reproduction characteristics, making it an ideal white light source.
- Research and develop III-nitride LEDs for direct white light emission technology.
- Research to improve LED luminous efficiency and light output, developing power-type LEDs. The luminous efficiency of traditional incandescent lamps is 16 lm/W, while fluorescent lamps have a luminous efficiency of 85 lm/W. Therefore, III-nitride LED white light lighting sources must achieve luminous efficiency exceeding 100 lm/W to replace incandescent and fluorescent lamps while also reducing costs.
8. Optical Disc Storage and Laser Ranging, Laser Printing, Laser Instruments. Optical disc storage and laser ranging, laser printing, and laser instruments are another significant application area for semiconductor lasers. The lasers used in CD (compact disc) and DVD (digital versatile disc) have wavelengths of 780 nm and 670 nm, 650 nm, respectively, and are used to “write” information onto optical discs or “read” sound or light signals from them. The shorter the wavelength of the laser, the higher the storage density of the optical disc. The InGaN laser with a wavelength of 410 nm can significantly increase the storage capacity of optical discs. The InGaAlP laser with wavelengths of 670-630 nm has replaced He-Ne lasers in many applications, finding significant use in laser ranging, laser printing, and laser medical instruments.
9. Military Applications of Semiconductor Lasers. The AlGaAs high-power laser with a wavelength of 808 nm serves as the pump light source for high-power YAG (Yttrium Aluminum Garnet) solid-state lasers, replacing the original xenon gas lasers, eliminating the need for large power supplies and cooling systems, making solid-state lasers more efficient, compact, high-performance, long-lasting, and low-cost, suitable for military applications such as laser radar and nuclear explosion simulation, as well as nuclear fusion research. The underwater light transmission window is at 590 nm, and the advent of blue-green lasers has opened the door for underwater communication. The most critical device in fiber optic gyroscopes, which help determine direction during rocket and aircraft flight, is the semiconductor super-radiant light-emitting diode.
10. Environmental Protection. In nature, gases such as water vapor, methane, ammonia, carbon dioxide, carbon monoxide, hydrochloric acid, bromic acid, and hydrogen sulfide have sensitive absorption peaks in the 1.5-2.0 mm range. InAsSb or GaInAsSb variable quantum well lasers can reach wavelengths in the 1.0-4.0 mm range, and the recently developed quantum cascade lasers can reach wavelengths of 4.0-17 mm. These various lasers covering the infrared to far-infrared range serve as environmental guardians for atmospheric monitoring and detection.
Future Development of Semiconductor Technology
1. Revolution in Information Technology. The explosive increase in information volume demands greater capacity for information channels. What is transmitted online includes not only text but also music, images, and television signals; it requires not only wired but also wireless communication; and it needs to cover not just intercontinental, international, and intercity communication but also local area networks. Therefore, new communication systems such as Integrated Services Digital Network (ISDN) and multimedia technologies need to be developed.
Information processing includes text processing, knowledge processing, image processing, language recognition, image recognition, and intelligent processing. Artificial intelligence has achieved certain human-like intelligence through computers, such as understanding and producing language, recognizing images, proving mathematical theorems, playing chess, composing music, and conducting professional assessments and medical diagnoses. Computers will liberate people from some daily mental labor and expand human wisdom to previously unimaginable levels through the application of “thinking tools.”
2. Higher Integration. The mainstream processes of integrated circuits will undergo four development stages: 65 nm (integrated circuit line width) in 2007, 45 nm in 2010, 33 nm in 2013, and 22 nm in 2016 for industrial production. To achieve this, a series of key technologies and specialized equipment must be resolved, such as the development of new devices (non-traditional CMOS devices, new types of memory, logic devices, etc.), IC design, packaging, and testing technologies, as well as new photolithography machines and etching machines.
The size of semiconductor devices cannot be reduced indefinitely. If the device size approaches the de Broglie wavelength of electrons (10 nm), quantum effects will become more pronounced, necessitating the design of new semiconductor devices based on quantum mechanics principles.
3. Development of Semiconductor Optoelectronic Devices Towards Longer and Shorter Wavelengths, Higher Power, and Higher Operating Frequencies. High-power laser arrays and quasi-continuous (QCW) devices, in addition to serving as pump sources for solid-state lasers, can also be directly used for material processing, medical applications, instrumentation, sensitive technologies, and printing, entering markets traditionally dominated by non-semiconductor lasers, replacing gas and solid-state lasers. AlGaN/GaN heterojunction bipolar transistors have good linearity, large current capacity, and uniform threshold current, primarily applied in high-power microwave systems that require high linearity and operate in harsh environments, such as military radar and communications; they can also be used in intelligent robotic systems operating in harsh conditions.
4. Integrated Optics and Integrated Optoelectronics. A system composed of lasers, modulators, waveguides, gratings, prisms, and other passive optical components integrated on semiconductor films is called an integrated optical system. Integrated optical systems replace electrical interconnections with optical interconnections, offering advantages such as wide bandwidth, large information capacity, low loss, high speed, parallel processing, and resistance to electromagnetic interference in computer and communication systems. Silicon materials are low-cost and have mature processes, widely used in microelectronic devices. However, since silicon is an indirect bandgap material, it cannot be used for light-emitting devices. Currently, scientists are working to solve the light source problem to achieve optoelectronic integration on silicon materials.
5. Semiconductor Superlattice and Quantum Wire, Quantum Dot Devices. Semiconductor superlattices, quantum wires, and quantum dots are low-dimensional structures that possess unique physical properties, such as quantum confinement effects and two-dimensional or one-dimensional characteristics of electron motion, allowing for the fabrication of high-performance devices such as lasers, high electron mobility devices, optical bistable devices, and resonant tunneling devices. As the size and dimensions of devices are further reduced, making the average free path of electrons greater than the device size, electrons will move coherently without being scattered by impurities or lattice vibrations. Utilizing these characteristics, it is expected to manufacture ultra-fast, ultra-low power electronic devices. For example, quantum dot single-electron transistors will significantly reduce the power consumption of dynamic random-access memory (DRAM).
6. Semiconductor Quantum Information Devices. Current processes can generate and detect single photons on semiconductor quantum dots, making semiconductor quantum dots the most promising solid devices for quantum information processing (quantum computing, quantum communication). The rapid development of quantum information science and technology provides revolutionary theoretical and experimental methods for precision measurement, quantum computing, and secure communication. The key to quantum information is the coherence of photons. Photons, as the most fundamental quantized entities in quantum theory, can easily achieve the entire process of collecting, transmitting, copying, storing, and processing information, possessing unique inherent advantages as carriers for quantum communication and quantum computing. Therefore, photon-based quantum information processing devices are the foundation of various quantum information engineering, and their fundamental principle research and fabrication will lead to a leap in computational science and communication capabilities.
7. Spintronic Devices. Currently, microelectronic devices use charge carriers to carry information. If a material can utilize both the charge and spin properties of charge carriers as information carriers, it could lead to the manufacture of devices with non-volatile, low power consumption, high speed, and high integration advantages, potentially causing significant changes in electronic information science. Dilute magnetic semiconductors doped with magnetic ions and spintronics have emerged to meet this requirement. Experiments have shown that the spin coherence time in semiconductors has reached the nanosecond level, far exceeding the coherence time of charge carriers, indicating the important application prospects of spintronics in future quantum computing and quantum communication. The main difficulty in achieving spin-based quantum computers is the precise control and maintenance of spin coherence, thus many physical problems need to be researched and solved regarding how to generate spin-coherent electronic states and reduce spin decoherence.
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